Hi,on my laptop (Lenovo Z50-75), I can set the backlight brightness via /sys/class/backlight/radeon_bl0/brightness, but xbacklight says "No outputs have backlight property".The hardware:A dual-graphics setup with the AMD FX7500 CPU with respective GPU and AMD Radeon R7 M255.Driver: open source radeon driver.xrandr --props|grep -i backlgives no outputHow can I make X find and use the back